1. Technical Field
The present disclosure relates to earphones and, particularly, to a carbon nanotube based earphone.
2. Description of Related Art
Conventional earphone generally includes earphone housing and a sound wave generator disposed in the earphone housing. The earphones can be categorized by shape into ear-cup (or on-ear) type earphones, earphones, ear-hanging earphones, for example. The earphones can be disposed in the ears of a user. The ear-cup type earphones and ear-hanging earphones are disposed outside and attached to the ears of a user. The ear-cup type earphones have circular or ellipsoid ear-pads that completely surround the ears. The ear-hanging type earphones have ear-pads that sit on top of the ears, rather than around them. The earphones can also be categorized as wired earphones and wireless earphones.
The earphone housing generally is a plastic or resin shell structure defining a hollow space therein. The sound wave generator inside the earphone housing is used to transform an electrical signal into sound pressure that can be heard by human ears. There are different types of sound wave generators that can be categorized according by their working principle, such as electro-dynamic sound wave generators, electromagnetic sound wave generators, electrostatic sound wave generators and piezoelectric sound wave generators. However, all the various types ultimately use mechanical vibration to produce sound waves and rely on “electro-mechanical-acoustic” conversion. Among the various types, the electro-dynamic sound wave generators are most widely used. However, the structure of the electric-powered sound wave generator is dependent on magnetic fields and often weighty magnets.
Carbon nanotubes (CNT) are a novel carbonaceous material having extremely small size and extremely large specific surface area. Carbon nanotubes have received a great deal of interest since the early 1990s, and have interesting and potentially useful electrical and mechanical properties, and have been widely used in a plurality of fields. The carbon nanotube film used in the thermoacoustic device has a large specific surface area, and extremely small heat capacity per unit area that make the sound wave generator emit sound audible to humans. However, the carbon nanotube film used in the thermoacoustic device has a small thickness and a large area, and is likely to be damaged by applied external forces.
What is needed, therefore, is to provide an earphone for solving the problem discussed above.